In component mounting machines for mounting electronic components on boards such as printed circuit boards, a sequence of mounting of object components is optimized for achieving shorter processing time (mounting time). Methods of the optimization often differ with specifications of component mounting machines; however, component mounting machines having a highly productive multiple placement head for sucking a plurality of components in a sucking step and mounting the components on a board have recently been developed due to a steep increase in demand for electronic equipment such as portable telephones and notebook PCs, and new methods of optimizing component mounting sequence that correspond to such high-function component mounting machines have been demanded.
Among conventional arts for such a purpose is a component mounting sequence optimizing method that improves an efficiency of suction of a multiple placement head capable of simultaneously sucking a plurality of components and that minimizes a moving amount of the multiple placement head (see Japanese unexamined patent application No. 2002-171097, for example). In accordance with the optimizing method, optimization of a component mounting sequence can be achieved that is suitable for the component mounting machine having the highly productive multiple placement head.
Flow from suction to mounting of components in the component mounting machine in the component mounting sequence optimizing method will be described with reference to a flowchart of FIG. 11. In a step S1, a plurality of components are sucked by the multiple placement head from component feeding sections. In a next step S2, the components sucked in the step S1 are conveyed to a recognition section and are then recognized. In a next step S3, one of the sucked components is conveyed to a mounting position. In a next step S4, the component conveyed to the mounting position in the step S3 is mounted onto a board. In a next step S5, a number of components still sucked on the multiple placement head is determined, and the step S3 and the step S4 are then repeated until all the sucked components are mounted. Herein, the step S1 will be referred to as a suction operation, and the step S2 as a recognition operation, the step S3 and the step S4 together as a mounting operation.
Since the operations of suction, recognition, and mounting are independent of one another as apparent from FIG. 11, and completion of the last operation precedes initiation of the next operation, a processing time can be therefore determined as a total length of time required for each of the operations. As for the mounting operation, the processing time is determined by a travel of the multiple placement head in the repetition of the conveyance to the mounting points and the mounting operation. In the conventional art, therefore, a component mounting sequence is determined so as to minimize the moving amount of the multiple placement head.
Herein, the “processing time” refers to a total time required for mounting of object components.
In the above conventional optimizing method, however, the recognition section for recognizing sucked components is provided separately from the multiple placement head as described above, and no consideration is given to a structure in which a head camera for component recognition is installed on the multiple placement head so as to allow conveyance and recognition of components to be performed in one step. Therefore, application of the conventional optimizing method described above to a component mounting machine in which the head camera is installed disables the characteristic of the head camera that allows the conveyance and recognition of components to be performed in one step.
In FIG. 12 is shown a working head in which the head camera is installed. As shown in FIG. 12, the working head 1 has a plurality of component suction nozzles 2 and one head camera 3, which stands by at the left or right end of the working head 1, propels itself along array directions 4 of the component suction nozzles 2, and recognizes a suction status of electronic components held on the component suction nozzles 2. With this configuration, the suction status of the components can be inspected while the components are conveyed by the working head 1.
Flow from suction to mounting of components in the component mounting machine in which the head camera 3 is installed will be described with reference to a flowchart of FIG. 13. In a step S11, components are initially sucked by the working head 1 from component feeding sections. In a next step S12, a component fed in the step S11 is conveyed to a mounting position and recognition of the components by the head camera 3 is started. In a next step S13, whether recognition of the component that is to be mounted has been completed or not is determined on the basis of a status of the component recognition and, if not completed, standby in the mounting position lasts until the recognition of the object component is completed. In a next step S14, the component conveyed in the step S12 is mounted on the board. In a next step S15, a number of components held by the working head 1 is determined. Then the step S12 (except the component recognition, which has already been started), the step S13, and the step S14 are repeated until mounting of all the components is completed.
As is evident, particularly from the step S13 shown in FIG. 13, the operations are not independent of one another, and the mounting operation is influenced by the recognition operation. Accordingly, a component mounting sequence that minimizes a travel of the working head 1 is not necessarily an optimal mounting sequence.
FIG. 14 shows a comparison of processing time between a component mounting machine in which the head camera 3 is installed and a component mounting machine in which the head camera 3 is not installed. Herein, characters “A,” “B,” and “C” represent components, “CONVEYANCE X” denotes a conveyance operation for a component X to a mounting position, “MOUNTING X” denotes a mounting operation for the component X, and “RECOGNITION X” denotes a recognition operation for the component X. The “X” denotes any of the “A”, “B”, and “C”. The conveyance X and the recognition X are required to be completed before the component X is mounted. With use of the head camera 3, as shown in FIG. 14, recognition time for components can be removed from processing time, and thus the processing time can greatly be reduced.
If a mounting sequence of A→B→C is changed to a mounting sequence of C→B→A on the basis of a reason that a travel of the working head 1 following the latter sequence is shorter than a travel of the same following the former sequence, a given length of time is still required for the component recognition for the components A, B, and C though a length of time required for the conveyance of the component C is reduced as shown in FIG. 15. Accordingly, the working head 1 is obliged to postpone starting the mounting of the component C until the component recognition is completed. Such simple determination of the mounting sequence according to amount of travel of the working head 1 may result in worse processing time because of addition of recognition time to the processing time.